The thrust ball bearing assemblies used in steerable vehicle suspension struts have fairly rigorous sealing requirements, because of the harsh environment to which they are exposed. It is also a great advantage in handling if such bearing assemblies are unitized, that is, if all the components are somehow retained together as a unitary assembly prior to installation to the vehicle. Several patents assigned to the assignee of the present invention disclose bearings in which the rigorous sealing and unitization features are combined in a simple structure.
One of the most simple is that disclosed in U.S. Pat. No. 4,400,041 to Lederman. An upper and lower metal race are stamped in a curvilinear shape that creates a pair of angular contact ball pathways, but which also leaves a pair of curved outer surfaces that need to be enclosed and sealed from the environment. The upper race is pushed into a concavity in an elastomer when it is installed, which also seals it. To seal the lower race, a continuous layer of elastomer is injection molded over its entire outer surface. The molded elastomer layer also forms a pair of sealing lips at the edges which engage the upper race to seal in the ball complement. One of the lips snap fits into a groove in the upper race to retain the races together, as well. While this design provides unitization, complete sealing, and a small number of components, a drawback is the cost of injection molding the elastomer layer to the lower race. The lower race must be carefully clamped and held in the mold to block elastomer from getting onto the ball pathway, which can be difficult if there is any variation in the race surfaces. It is much easier to mold an elastomer part as a separate piece, as opposed to molding it directly to a metal part. However, the least expensive means of molding a plastic part, called bypass molding, requires access windows through the part in order to mold surfaces that would otherwise radially overlap, like latches. These access windows would prevent complete sealing.